Sea Levels Rising Fast on U.S. East Coast | Charles Q. Choi

Not clear whether human-caused global warming is to blame, experts say.

The last house on Holland Island, Maryland, where 360 people lived before tides took over (file picture). Photograph by Astrid Riecken for the Washington Post/Getty Images

June 25, 2012 (National Geographic) -- Sea level rise on the U.S. East Coast has accelerated much faster than in other parts of the world -- roughly three to four times the global average, a new study says.

Calling the heavily populated region a sea level rise hot spot, researchers warn that cities such as Boston, New York, Philadelphia, and Baltimore could face a more flood-prone future.

(Also see "New York, Boston 'Directly in Path' of Sea Level Rise.")

Sea levels worldwide are expected to rise as global warming melts ice and causes water to expand. Those levels, though, are expected to vary from place to place, due to factors such as ocean currents, differences in seawater temperature and saltiness, and the Earth's shape.

Now it seems scientists have pinpointed just such a variance.

READ MORE: National Geographic